Cancer cells expressing high levels of Bcl-2 are resistant to apoptosis induced by MiTMABs. A-B, Asynchronously growing HeLa, HT29, SW480, MCF-7 and H460 cells were treated with the indicated concentration of OcTMAB for 48 h. Cells containing <2N DNA content (mean ± S.D. from two independent experiments) were determined by flow cytometry (A) and the presence of cleaved PARP was assessed by immunoblotting (B). C, Expression levels of the Bcl-2 family members, Bcl-2, Mcl-1 and Bcl-XL, were assessed and compared in the indicated cancer cell lines by immunoblotting. β-actin served as a loading control.